$( "#upload_conf_file_button" ).click(function(e) {
    e.preventDefault();
    var formData = new FormData();
    // formData.append(file input name, files);
    formData.append('file', $('#upload_conf_file_input')[0].files[0]);
    
    $.ajax({
           url : '/upload_conf_file',
           type : 'POST',
           data : formData,
           processData: false,  // tell jQuery not to process the data
           contentType: false,  // tell jQuery not to set contentType
           success : function(data) {
               console.log(data);
               alert(data);
           }
    });
    alert('uploadfile')
  });



//  submit and download use different action
$('#submit').click(function () {
    var form = $('#uploadFile')[0]; // You need to use standard javascript object here
    var formData = new FormData(form);

    // form validation
    if ($("#uploadFile").valid()) {
        $('#processing_layout').css({ 'background-color': 'rgba(128, 128, 128, 0.329)', 'height': '100%', 'width': '100%', 'display': 'block' })
        $('#processing_image').css({ "display": 'block' });
        $.ajax({
            url: $('form').attr('action'),
            type: $('form').attr('method'),
            // async: false,
            data: formData,
            contentType: false,
            processData: false,
            success: function (data) {
                $('#processing_layout').css({ "display": 'none' });
                $('#processing_image').css({ "display": 'none' });
                $('#log-panel').css({ 'display': "block" })
                logContent = data;
                logContentRegx = /\\r\\n|\r\n/g
                $('#log-content').html(logContent.replace(logContentRegx, '\n'))
                // output*  mode : download file, button enable
                // insert* mode : no file to download, so button disable 
                insert_Regx = /^insert/
                if (! insert_Regx.test($('#mode_name').val())){
                    $('#download').prop('disabled', false);
                    $("#a-download").css({ "pointer-events": 'auto' })
                }
            },
        });
        return false;
    } else {
        // do your logic
        return false;
    }
});